How do they test complex systems like the SCADA controllers used in cars?

[e100]

In the early stages of testing there's a high risk of blowing up an engine or running off the road which makes physical testing expensive and dangerous.

Does that mean they have to build a software emulator that models the behaviour of the whole car just so they can get the software quality to a point where it is safe to test using the actual hardware?

[SerieZ]

Regarding the electronics each and every PCB is ICT,Functional and HASS tested by their Supplier with every part being traceable.
I am very certain they also do a functional test (emulation) before giving it to a test driver and they will certainly test every single car during regular production.